Methods for encoding and decoding images, corresponding encoding and decoding devices and computer programs

摘要

A method is provided for encoding an image represented by a sequence of symbols. The method includes the following steps: defining subsequences within the sequence; and going through the subsequences applying the following sub-steps for a routine subsequence: determining an adjacent routine encoded group including two previously encoded subsequences, one of which belongs to an adjacent encoded group associated with a subsequence that is separate from the routine subsequence; initializing a routine probability of occurrence of a symbol, taking into account two known probabilities of occurrence of the symbol, relating to two previously encoded subsequences of the adjacent routine encoded group; the consecutive entropic encoding of the symbols, and updating the routine probability of occurrence; and storing the routine probability of occurrence after encoding the last symbol.

主权项

1. A method for encoding at least one image represented by a sequence of symbols generated according to a predetermined encoding scan order, wherein the method comprises the following steps:
determining sub-sequences in each sequence, a sub-sequence comprising a predetermined grouping of symbols; and scanning determined sub-sequences comprising the following sub steps for at least one current sub-sequence and for at least one context, wherein at least one step is performed by a processor device:
determining a neighboring group comprising a least two previously encoded sub-sequences, called a current encoded neighboring group, amongst which at least one belongs to an encoded neighboring group associated with a sub-sequence, distinct from said current sub-sequence, said distinct sub-sequence not belonging to said encoded neighboring group of the current sub-sequence, and said current sub-sequence not belonging to the encoded neighboring group of said distinct sub-sequence;initializing at least one probability of appearance of a symbol associated with the context, called a current probability of appearance, taking account of at least two probabilities of appearance of said symbol, called known probabilities of appearance, relative to two previously encoded sub-sequences of said current encoded neighboring group;successive entropy encoding of said symbols according to said predetermined encoding scan order and, for each symbol, updating of said current probability of appearance for the context associated with said symbol; andstoring said current probability of appearance of said encoded symbols in the current sub-sequence in a computer-readable memory, after encoding of the last symbol of said current sub-sequence.